This invention is generally directed to red developer compositions, and the use of these compositions in electrostatographic imaging systems. More specifically, the present invention is directed to positively charged single component red developer compositions comprised of resin particles, specific classes of red pigments, charge enhancing additives, and additive components. The aforementioned developer compositions are particularly useful in the electrostatographic imaging systems as illustrated in Hays U.S. Pat. No. 4,459,009, the disclosure of which is totally incorporated herein by reference.
Toner compositions with charge enhancing additives are generally known. Thus, for example, there is disclosed in U.S. Pat. No. 3,893,935 the use of certain quaternary ammonium compounds as charge control agents for electrostatic toner compositions. This patent teaches the incorporation of a specific quaternary ammonium compound into toner compositions for the purpose of obtaining particles exhibiting relatively high uniform and stable net toner charge when mixed with a suitable carrier vehicle. A similar teaching is disclosed in U.S. Pat. No. 4,079,014 with the exception that a different charge control additive is selected, namely, a diazo type material.
Further, there are described in U.S. Pat. No. 4,298,672 developer compositions containing as a charge enhancing additive an alkyl pyridinium compound including, for example, cetyl pyridinium chloride. Other patents disclosing toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; and 4,394,430. Also, there are illustrated in U.S. Pat. No. 4,560,630, the disclosure of which is totally incorporated herein by reference, developer compositions with distearyl dimethyl ammonium methyl sulfate charge additives; and in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developers containing as charge enhancing additives various sulfate and sulfonates.
Also known are colored developer compositions, reference for example U.S. Pat. No. 4,562,135, which discloses positively charged toner compositions with chromophores. Further, illustated in copending application U.S. Ser. No. 764,024 are positively charged toner compositions with first and second resin particles, a charge enhancing additive, and pigments such as cyan, magenta, and yellow.
Moreover, there are described in U.S. Pat. No. 4,443,527 colored magnetically attractable toner powders without charge control additives containing a magnetic core, a masking layer enveloping the core and coloring agents, inclusive of Pigment Red 49, Pigment Red 49:1, and Pigment Red 49:2 present in/or on the masking layer. Other examples of coloring agents illustrated in the '527 patent include insoluble azo pigments such as toluidine red, naphthol red pigments, Pigment Red 17, Pigment Red 31, and perylene pigments, see column 4, beginning at line 16. Also, in U.S. Pat. No. 4,530,893 there is disclosed one component red colored magnetic developer containing a specific magnetic powder, a red azo pigment, different than the pigments of the present invention; and a binder resin, reference column 2, beginning at line 31. In U.S. Pat. No. 4,563,409 there are described positively charged toners obtained by mixing a coloring agent such as a dyestuff or pigment with a synthetic resin wherein the dyestuff apparently functions as a coloring agent, different than the pigments of the present invention; and an electric charge controlling material, see column 1, beginning at line 47. Other patents of background interest include U.S. Pat. Nos. 3,652,438; 3,781,208; 3,933,664; 4,051,052; 4,145,299; 4,414,320; 4,258,116; and 4,431,721.
Single component toners are disclosed in a number of publications. These toners are generally comprised of toner resin particles and magnetite. Also, recently there was developed an apparatus for charging toner particles comprised of a charging means, and a transporting means as illustrated in U.S. Pat. No. 4,459,009, the disclosure of which is totally incorporated herein by reference. Toners can be charged in this apparatus in a zone situated between the charging means, and transporting means. These toners are, however, charged negatively, or the charges thereon are of a rather low positive polarity thus rendering them unuseful in many situations. Therefore, there is a need for toners, especially colored toners which can be charged positively in the aforementioned apparatus. More specifically, there is a need for red toners that will charge to a positive polarity of a sufficient effective magnitude in the apparatus of the '363 patent. There is also a need for positively charged red toner compositions that are useful in electrostatic imaging processes wherein they enable images of excellent resolution with substantially no background deposits. Moreover, there is a need for positively charged red toner compositions that retain their triboelectric charge for an extensive period of time, which compositions are particularly useful for developing images generated on a layered photoconductive device charged negatively, such as the devices described in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. There is also a need for single component red toners that can be charged to a sufficient specific positive polarity thereby minimizing background development which occurs with several prior art toner compositions wherein the positive charge is of a lower value. Thus, for example, when the positive charge is below about 10 microcoulombs per gram, there results with the developer selected subsequent to their utilization in an electrostatographic imaging apparatus, images with increased background deposits thereby undesirably permitting a reduction in image resolution. Additionally, there is a need for toner compositions wherein the positive charge is not significantly high, that is for example exceeding 30 microcoulombs per gram since in such instances the toner compositions cannot usually be efficiently transferred to the photoreceptor surface. There is also a need for single component red toners that can be effectively transferred to paper substrates from the photoreceptor subsequent to development thereby enabling images of acceptable optical densities. Thus, reflection optical densities of greater than 0.90 as measured on a Macbeth Densitometer with either yellow or green filters are obtainable with the developers of the present invention. Moreover, there is a need for toner compositions with melting characteristics to enable permanent fusing of the resulting toner to the image surface, and wherein such toner compositions do not agglomerate on standing. Both melting and blocking characteristics can generally be obtained with toner compositions comprised of resins that have glass transitions greater than about 50.degree. C. but less than about 65.degree. C.